The role of genetic factors in the between subject variation in the response to dental caries will be studied using the salivary peroxidase model. Genetically determined structural heterogeneity in peroxidase will be compared with differences in salivary antibacterial activity and dental caries scores in humans. Initial phases of the study will comprise establishment of reliable measures for easy detection of the structural variation in the enzyme and differences in antibacterial activity. Electrophoretic and chromatographic procedures will be used to modify existing methods such that easier typing of all subjects will be possible. Existing measures of antibacterial activity will be adapted to allow tests to be made against microorganisms implicated in dental caries (e.g., S. mutans). Antibacterial activity and peroxidase typing will be correlated with dental caries scores in a population with varying responses to dental caries, using a three way analysis of variance. This research is of significance in: 1) understanding the role of genetic factors in the individual variation in response to dental caries; 2) further elaborating the evolutionary significance of the peroxidase polymorphism; and 3) in providing the clinician with a potential tool for genetic typing of individuals especially susceptible or resistant to dental caries.